Method and system for use in monitoring biological material

ABSTRACT

A method and system for measuring metabolic gas concentration. The method includes: applying, via a tunable coherent infrared light source, an infrared light beam to a region of interest, wherein the region of interest is positioned between the tunable coherent infrared light source and a detection module, wherein the region of interest is in fluid communication with a biological material including living cells emitting a metabolic gas; measuring, via the detection module, a plurality of signals based on the application of the infrared light beam to the region of interest, wherein measuring each of the plurality of signals further comprises tuning the tunable coherent infrared light source; and determining the concentration of the metabolic gas based on the plurality of signals.

TECHNOLOGICAL FIELD

The present invention in the field of monitoring the condition/status ofa biological material, and relates to a method and system for detectionof microorganisms and living cells in a biological material by opticalmeasurements of metabolic gases.

BACKGROUND

Monitoring the live biological activity in a biological material isneeded in various industries, for example in the medical field formonitoring microorganisms contaminants in blood/blood-components, infood and beverages (F&B) industries, and in pharmaceutical industriesfor example for monitoring fermentation processes.

Conventional techniques for monitoring biological activity in abiological material generally include direct techniques such as: viablecount in which a diluted samples are grown on agar medium dish; stainingor microscopy; pH and glucose measurements; swirling; and opticaldensity (OD) measurements in which a sample of the biological materialtaken in to a cuvette and the level of microorganisms is determinedoptically based on turbidity of the sampled biological material itself.Other known techniques utilize monitoring the biological activityindirectly, for example based on analysis of gases consumption (such asdissolved oxygen—dO₂) or accumulated (such as carbon dioxide —CO₂) in asample of the biological material. In those techniques, a sample of thebiological material is incubated for a period of time to allowconsumption or accumulation of gases by live microorganisms contained inthe sample and then the metabolic gases are analyzed chemically and/orby utilizing spectroscopic measurements. However, conventional directmeasurements made on samples of the biological material are invasive(thus increasing the risk of contamination of the biological material),time-consuming, and do not enable real-time monitoring of the growingpopulation. Direct measurements such as for dO₂ may be also inaccurate.For instance, in fermentation processes involving fungi, the diffusionof oxygen through the substrate does not occur at a uniform rate andtherefore measurements with dO₂ electrodes when performed at loweroxygen diffusion rate may be misleading. Also, oxygen is a decreasingparameter that is limited by zero. Other, conventional, IR based,indirect techniques based on gas analysis in the container including thebiological material are often influenced by the local conditions insidethe container (e.g. temperature, pressure, humidity) and may lead toinaccurate measurements.

GENERAL DESCRIPTION

There is a need in the art for a novel technique for in-situ, real-time,noninvasive and accurate monitoring of biological materials, enablingthe detection, monitoring and/or controlling of microorganisms andliving cells in a biological material, such as blood components, foodproducts and/or biological materials used in fermentation processes, forexample those used in the pharmaceutical and/or food and beverages (F&B)industry. Specifically there is a need in the art for an in-situreal-time non-invasive accurate technique for detection ofmicroorganisms in a culture media utilizing measurement of gaseousproducts generated during living cells growth/proliferation.

The known techniques for detecting metabolic gas concentrations in-situare generally not sensitive and precise enough for correlate with biogrowth of the microorganisms and living cells in biological material.The known techniques for detecting microorganisms' contaminations and/orgrow in biological material by spectroscopic measurements of metabolicgas concentrations are generally not suited and/or are in-capable ofin-situ real time operation. This is mainly because these techniques areinvasive with respect to stored biological material that has to beinspected, i.e. they require sampling and incubation of the biologicalmaterial in a separate sealed incubation container (sampling vial) whichis impermeable for gases and possibly contains certain growth media. Tothis end, the conventional techniques utilize sampling/transferringcertain amount of the biological material from a sealed container inwhich it is stored/maintained into a suitable sampling vial/container,which is specifically designed/selected to facilitate the spectroscopicmeasurements of metabolic gas(es). Conventional sampling vials used forthis purpose are generally non-permeable to the metabolic gas in orderto enable accumulation of high concentrations of the gas in the samplingvial. The conventional sampling vials are also specifically configuredfor the spectroscopic measurements (e.g. formed with specificallyselected materials having high transitivity to wavelengths used inmeasurements). The sampled biological material is maintained in thesampling vial for sufficient time (the detection limit is only afterincubation time of between 18 to 48 hours) for consumption oraccumulation of relatively low or high concentrations, respectively, ofgas consumed or accumulated by microorganisms contained in thebiological material. As indicated above, many of the known techniquesfor growing biological material use incubation of a test sample whileproviding suitable growth conditions (e.g. providing growth medium suchas agar, and/or incubating conditions/temperatures, and/or sufficienttime for growth) to accelerate the microorganisms growth and accordinglyaccelerate production of the metabolic gases by the microorganismscontained in the sample. This is in fact because the sensitivity and/oraccuracy of the known spectroscopic metabolic gas detection techniquesrequire consumption or accumulation of relatively low or highconcentrations, respectively, of the gas for the detection thereof.

The known techniques are thus not suited for in-situ real timenon-invasive, accurate monitoring of biological activity/microorganismsin a biological material mainly because (1) they are invasive, i.e.require sampling of the biological material, (2) require specificequipment, i.e. the sampled biological material is transferred into aseparate, specifically designed, sealed sampling vial (e.g.non-permeable to metabolic gases, highly transmitting for wavelengthsused in spectroscopic measurements, e.g. containers made ofglass/quartz), as well as typically require use of specific growthmedia, and (3) they are time consuming as they typically requirerelatively long incubation periods (e.g. 18-48 hours) of the sampledbiological material for accumulation of sufficient(measurable/detectable) concentrations of the metabolic gases.Non-invasive gas monitoring methods available are not sensitive enough.In fact, in-situ, real time and non-invasive high resolution monitoringof biological activity in biological substances are needed in variousfields. Specifically, such traits are needed in medical fields forhandling blood and blood components for monitoring the blood/componentsthereof (e.g. prior to blood transfusions). Also such traits are highlyneeded in various fermentation processes in which sensitive, real-timemonitoring of the biological activity may provide substantial increasein the yield of the fermentation process. This would allow thecontrol/monitoring of cells growth of a wide variety of microorganisms(including non-transparent and pathogenic ones), within various medium(including high turbidity/viscosity medium), early stage detection ofcell growth, shorter R&D cycle time, and real time monitoring of biomassproduction process for increasing the yield (e.g. by determining optimalseed transfer and induction times, controlling thegrowth-media/biological-material composition utilizingcontrolled-depletion of nutrients, etc).

Specifically, one application of the invention is to detect bacterialcontamination of a blood or blood-components, such as red blood cells,plasma and platelets, which are commonly used for transfusions.Particularly the invention provides for real time in situ non-invasivemonitoring of microbiological contaminants in blood platelets which area component of blood that is involved in blood clotting.

Allogenic blood/blood-components for transfusion are a potential sourceof infection by a variety of known and unknown transmissible agents.Over the last three decades, the risk of transfusion-relatedtransmission of viral diseases such as human immunodeficiency virus(HIV) I/II, hepatitis C virus (HCV), hepatitis B virus (HBV) and humanT-lymphotropic virus (HTLV)/II has decreased dramatically. With bloodproducts now being routinely screened by ultrasensitive techniques tominimize the risk of transmitting viruses to recipients, the known riskof transmission of bacteria has emerged as the greatest residual threatof transfusion-transmitted disease.

Bacterial contamination has proved more difficult to address than viralcontamination, and remains the most prevalent transfusion-associatedinfectious risk.

This is especially true for platelets, which are stored at roomtemperature (20-24° C.) for up to five days (rather than the previouspractice of storage for up to seven days), in bags that are permeable tooxygen and carbon dioxide, and under sufficient constant agitation toprovide adequate oxygenation, to prevent platelet aggregation and tomaintain optimal platelet viability and functional properties.

Storage of the platelets at optimal metabolic conditions, at roomtemperatures, and with agitation in bags/containers permeable to O₂ andCO₂, promote ongoing bacterial proliferation throughout the storageperiod and thus increase the risk of transmitted bacteria and bacteremiain the patient. The risk of bacterial contamination in platelets isestimated to be one in 1500, which is 50 to 250 times higher than thecombined risk of viral infections.

As described above, the conventional techniques for testing plateletsfor contaminants prior to transfusion are invasive (require opening ofthe sealed blood storage container for sampling thus increasing the riskof inadvertent contamination of the remaining platelets), requirespecific equipment and possibly growth media, and time consuming. Sincethe conventional techniques do not provide real time—pre transfusionreliable testing for contamination in platelet bag, the practical shelflife of platelets is decreased (from seven to five days) to avoid anincrease in bacteria concentration to a levels that can cause sepsis inrecipient.

In this connection, the present invention allows for in-situnon-invasive (without opening the container and withdrawing a portion ofthe biological material) real time and sensitive monitoring of abiological material, such as (but not limited to) a blood component,that can serve, intentionally or unintentionally, as a growth medium forthe growth of microorganisms such as bacteria, and that is containedwithin a container sealed with respect to the biological material. Thepresent invention provides for monitoring any biological material, suchas food, human or animal tissues, and cell cultures, with particularapplication to blood components such as platelets. The technique of thepresent invention allows for detecting bacterial contamination inplatelets contained/stored in conventional platelet storage bags (e.g.plastic bags) based on quantitative analysis of metabolic gases, such asCO₂, released by bacteria inside the platelet plastic storage bag whichis permeable to metabolic gases, while the plastic storage bag with theplatelets remains sealed to contaminates. Furthermore, as it will beexplained in more details below, the detection of metabolic gas in thesealed container when performed according to the method of the presentinvention does not require a control/reference sample.

The concentration of the metabolic gas in a dead space associated withthe storage bag is monitored by optical/spectroscopic measurementsperformed according to the technique of the present invention asdescribed in more details below. The dead space, for the purposes of theinvention, is a space/region which is free of the biological materialunder inspection and is in fluid communication therewith. In someembodiments, the dead space is defined by a region/portion of thecontainer above a portion thereof containing the biological material. Insome other embodiments, the dead space is defined by a gaschamber/reservoir/pipe connectable to the container (e.g. in a mannermaintaining the sealing of the container), so as to be in the fluidcommunication with biological material in the container. Suchreservoir/pipe may be formed by a separate cavity configured as anextension of the dead space in the container.

The measurements of metabolic gas concentration may for example utilizespectroscopic measurements in mid-IR spectrum of light at wavelength(s)overlapping with strong absorption line(s) of a metabolic gas (e.g. CO₂or other metabolic gases). The light is transmitted through a part (deadspace) of the plastic bag that is above the stored platelets, and isappropriately detected by an IR detector. The spectroscopic technique ofthe invention provides for determining the concentration of CO₂ or othermetabolic gas by measuring light absorption within the plastic bag,while allows for discarding/discriminating the absorbance of the plasticbag itself, thus enabling in-situ monitoring of the metabolic gasescontained in the dead space of the bag.

The technique of the invention allows the detection of differenttransfusion—relevant contaminating bacterial species. This approachprovides on-line measurement of respiratory gases such as CO₂ at ambientatmospheric concentrations without the need for any pre-concentration orgas separation. The method is non-invasive since it does not requireopening the plastic platelet bag for examination. This non-invasivebacterial detection method represents a new approach to prevent thetransmission of bacterial contamination of platelets with an advantageof the method is that all measurements can be performed in real time,until right up to the time of transfusion and therefore the risk forsample errors is reduced to a minimum and the platelets' storage time isextended. Also, unlike conventional methods, the method of the presentinvention can be used with containers that are sealed with respect tothe biological fluid, and are either impermeable or are permeable to themetabolic gas(es) being monitored. Some other possible applications ofthe invention include real-time, precise monitoring of fermentationprocesses. Owing to the specific features of the method and device ofthe invention, the monitoring is made possible for any kind ofmicroorganisms (even pathogen) and any kind of culture medium (eventhose with high turbidity and/or viscosity). This allows thestandardization of the monitoring procedure for any kind of fermentationprocess. In fermentation, the biological material generally added to thegrowth medium. Specifically for example, fermentation processes are usedin the pharmaceutical industry for generating various biologicalsubstances such as: microbial cells (such as E. coli); microbial enzymes(catalase, amylase, protease, etc); primary metabolites (ethanol, citricacid, glutamic acid, etc); secondary metabolites (antibiotic,recombinant products: insulin, hepatitis B vaccine, interferon, etc).

The technique of the invention allows the detection of differentmicroorganism's species including: aerobic & anaerobic; transparent &non-transparent; and pathogenic microorganisms. This approach provideson-line high resolution measurement of respiratory gases such as CO₂ atambient atmospheric concentrations without the need for any incubation,gas separation, drying system or calibration. The detection method andsystem of the invention can apply qualitative and/or quantitativeanalysis and estimation of a level of biological activity ofmicroorganisms, for example in agar plates, and monitoring of biologicalactivity such as in the case of measuring living cells growth in theproduction of pharmaceutical products or proteins. Microorganisms areused commercially to produce foods (such as vinegar, yogurt, cause beerand wine spoilage), antibiotics and chemicals such as ethanol.Production of some of the most important and complex pharmaceuticalssuch as insulin, hormones, antibodies, or other proteins is carried outusing microorganisms (such as E. coli) that have been modifiedgenetically using recombinant DNA technology. From the early stages ofcommercial production of recombinant proteins and other pharmaceuticalmaterial, the handling of cultures has been subject to challenges. Oneof these challenges is how to cope with the problem of instability ofproduction processes as in the case of recombinant organisms andinduction. Commercial production of products on a large scale,especially in the pharmaceutical industry using fermenters, dependsheavily on the stable maintenance of the organisms during production andharvesting time. The fermentation process of recombinant bacteria needsto be precise and the cells concentration has to be monitored.

For clarity, in the following description, monitoring of pharmaceuticalfermentation processes for generating proteins is specificallydescribed. However it should be understood that the present inventioncan be used for real time monitoring of other fermentation processes inthe pharmaceutical industry and/or in the F&B industries.

In fermentation, specific microorganism species are deliberatelyintroduced into a fermentation container containing a biologicalmaterial serving as growth medium. The fermentation container is kept atsuitable conditions (e.g. glucose, yeast, agitation, temperature)encouraging the production of the desired biological substances/proteinsby microorganism. Typically, a gas inlet is coupled to a fermentationcontainer to supply suitable atmospheric conditions for themicroorganisms' metabolism (e.g. supply of ambient air) and a gas outletis also coupled to the fermentation container to evacuate gas which isricher in metabolic gases generated by the microorganisms' metabolism.In many cases, fermentation processes are monitored by occasionallycollecting a sample from the biological material in the container andanalyzing that sample (such as OD measurements) in order to determinedata indicative of the amounts of microorganisms and/or the amount ofthe produce material or proteins in the sample, and utilize that datafor controlling the fermentation process.

The amount of the biological substance, which is to be produced in thefermentation, is generally correlated with the amount/the rate of changeof the amount of microorganisms in the biological material in thecontainer. To this end, an accurate real-time monitoring of the amountof microorganisms enables accurate control over the fermentation processand provides for significantly increasing the yield of the product to beproduced.

For example, the production of recombinant protein is correlated with anoptimal induction process and microorganisms' amount. During the firststage, log (logarithmic) phase, the microorganisms is being grown tocertain, very specific, well define amount in which an inducer added tothe culture media. Then at a later/second stage, the recombinantbacteria stops proliferating and use their “cell energy” for theproduction of the recombinant protein. Problems that may occur duringbacteria log phase (due to problems with nutrients, for example), lackof precision during induction and/or over grown of the bacteria may leadto lower yield. Thus, by monitoring a time profile of the amount ofmicroorganisms and/or changes thereof, the fermentation process can becontrolled to improve the yield of the generated product and harvestingtime (see FIG. 9).

However, the conventional techniques for monitoring biomass infermentation processes are not performed continuously and are incapableof being carried out with high sensitivity in real time, and typicallyinvolve occasional collection of samples from the fermentation containerand examining these samples by techniques such as optical/criticaldensity measurement, viable counts, and by measuring the producedmaterial. These results, inter alia, in that the optimal time points forcollection of fermentation yield are often missed.

The present invention provides for an accurate real time andcontinuous/periodical monitoring of fermentation process bycontinuous/periodical monitoring of the atmospheric conditions in thecontainer to determine data indicative of a rate of metabolic gasproduction by microorganisms contained therein, or a change in such rateof production, and thereby determining the amount of the microorganisms,biomass, or the rate of change in this amount. The later are processedto control the fermentation process accurately in time such as toimprove the yield. For example the monitored amount of microorganismsand/or rate of change thereof may be compared with a referencedata/model to control the fermentation conditions (e.g. temperatures ofthe fermenter, gaseous atmosphere therein, nutrients or other materialssupplied during the fermentation process etc), and/or identify a time atwhich the fermentation process transit from the “first” (productionstage) to the “second” (“proliferation stage”) stages, for stopping,harvesting or managing the process at this time.

The system of the present invention may be configured to continuouslyand/or periodically/repeatedly monitor the gas/atmosphere in thefermentation container and may be in optical communication with the gaswithin the container itself (e.g. above the biological material) and/orin optical communication with a gas flowing out from the fermentationcontainer (e.g. gas being in fluid communication with the inside of thecontainer, for example gas flowing through the gas outlet of thecontainer).

Yet another attractive application of the present invention is relatedto detection of isotopologues of metabolic gases. Isotopologues aremolecules that are identical except for their isotopic composition.Examples of the isotopologues of carbon dioxide are ¹²C¹⁶O₂, ¹³C¹⁶O₂,¹⁶O¹²C¹⁸O, ¹⁶O¹³C¹⁸O. The natural abundance of isotopologues thatcontain a rare isotope is negligible in comparison to the commonmolecule. For example, the natural abundance of ¹³C¹⁶O₂ is 0.0111%, andthe natural abundance of ¹⁸O¹³C¹⁸O is 10-8. Different isotopologues ofthe same molecules have different vibration frequencies, and thusdifferent absorption spectra in the IR region. For example, molecules of¹³C¹⁶O₂ have a strong absorption at 2270.29 cm⁻¹, while the absorptionstrength of the nearest absorption line of ¹²C¹⁶O₂ at 2277.427 cm⁻¹ isweaker by a factor of about 30 than that of ¹³C¹⁶O₂. This provides meansfor discrimination between different isotopologues of the same moleculesby means of infrared absorption spectroscopy. In particular, a typicaltunable QCL operating in continuous wavelength (CW) mode can have a beamspectral width as narrow as 0.01 cm¹. That provides means forunambiguous measurement of concentrations of isotopologues of a moleculeunder study in a setup as described above. Isotopologues can serve asbiomarkers to trace particular metabolic processes. One example of suchan application is the use of D-glucose-¹³C₆ as a carbon based nutritionsource for bacteria for checking specific metabolic processes, that inturn can be used for example to study the efficiency of the fermentationreaction of glucose for ethyl alcohol production at different stages ofthe fermentation process.

Thus, the present invention provides a novel system and method forin-situ nondestructive (non-invasive) real time detection ofmicroorganisms in biological materials.

It should be understood that the term biological material herein relatesto any material that can serve as culture media for growth ofmicroorganisms and/or living cells. In this regards, this term includesand is not limited to blood and blood components such as platelets, F&Bproducts and biological materials used in fermentation processes (e.g.in the F&B and/or pharmaceutical industries). Also the termmicroorganisms relates to any living organisms such as bacteria, fungietc. The term metabolic gas relates to one or more gases produced orconsumed by microorganism's metabolism, and may include for examplegases such as carbon dioxide (CO₂) produced during respiration. Some notlimiting examples of gases that are specifically included in thisdefinition are carbon dioxide, oxygen, ammonia, hydrogen sulfide,methane, ethane, butane, ethylene, sulfur dioxide, carbonyl sulfide andnitric oxide. Examples of gases that are specifically excluded from thisdefinition include argon and inert gases such as helium or nitrogenwhich do not participate in the metabolic process. For clarity, in thefollowing description, the present invention is described specificallyin relation to the carbon dioxide metabolic gas. Nevertheless it shouldbe understood that the technique of the present invention is not limitedto carbon dioxide and can also be applied to detection microorganismsbased on other metabolic gases.

It should further be noted that the term in situ in the context of thecurrent disclosure refers to detection of microorganisms being performeddirectly on metabolic gas(es) formed in the originalstorage/fermentation container (at times termed herein as biologicalmaterial (BM) container), without sampling or opening the BM container.To this end, the detection is performed without a need to expose thebiological material in the container to external microorganisms. In thisregards, the term in-situ measurement should be interpreted broadly, asincluding analysis of the gas(es) directly inside the storagecontainer/bag of the biological material, where the term directlysignifies applied to gas(es) in a dead space being in fluidcommunication with the biological fluid in the storage container, namelya portion of the container itself or a reservoir/pipe non-invasivelyconnectable to said portion of the container. For example, metabolic gasdetection may be performed at the gas outlet of a fermentation containerand/or at a certain gas reservoir connectable to a BM container ofblood/blood-components (e.g. bag/vial) by a fluid connection that doesnot permit external microorganism contaminant into the BM container(e.g. utilizing a transfusion needle to connect thegas-chamber/reservoir to the BM container to allow gas flow to thereservoir without opening the BM container.

In this regards, the detection is non-invasive and nondestructive in thesense that measurement procedure does not destroy or affect in any waythe biological material, and thus the biological material can still beused for its original purpose, after the detection procedure. Thedetection is real-time in the sense that no incubation period isrequired and the results of the detection can be obtained within arelatively short time scale (seconds or minutes).

The goal of the detection is to determinate the presence ofmicroorganisms such as bacteria (e.g. bacteria contamination) in thebiological material. Yet it can be quantitative analysis and estimationof level of biological activity of microorganisms for example in agarplates and also monitoring of biological activity of microorganisms suchas in case of fermentation process.

Thus, according to one broad aspect of the invention, there is provideda method for use in detection of microorganisms in a biologicalmaterial, the method comprising:

(i) applying non-invasive in-situ optical measurements to a region ofinterest being a dead space free of a biological material and in a fluidcommunication with a portion of a container containing the biologicalmaterial, wherein said optical measurements comprise illuminating saidregion of interest with light of a including at least first and secondpredetermined wavelengths of substantially narrow spectrum correspondingto respectively an absorption peak of at least one metabolic gas and aspectral region outside the absorption peak of said at least onemetabolic gas, and measuring transmission of said first and secondwavelengths through said dead space; and

(ii) analyzing measured data of said transmission and generating dataindicative of a concentration of the at least one metabolic gas in saiddead space which is in the fluid communication with the biologicalmaterial, said generated data being thereby indicative of microorganismsin the biological material.

The measurements of metabolic gas concentration may generally beperformed utilizing infrared and/or visible portions of electromagneticradiation.

According to some embodiments of the present invention the methodfurther includes processing the data indicative of the concentration ofthe at least one metabolic gas utilizing equilibrium condition between arate of generation or consumption of the at least one metabolic gas bythe microorganisms and a rate of flow of the at least one metabolic gasinto and/or out of the container. Then utilizing the equilibriumcondition data about the microorganisms in the biological material isobtained/determined.

According to some embodiments of the present invention the spectralwidth of the substantially narrow spectrum of the first wavelengthoverlaps and exceeds a spectral width of an absorption line of saidmetabolic gas. Also, in some cases, the spectral width of the firstwavelength is less than a spectral distance between two spectrallyadjacent absorption lines of the metabolic gas.

Moreover in some cases the spectral separation between the first andsecond wavelengths of the light source is substantially small such thatthe first and second wavelengths are characterized by same or similartransmission through predetermined materials used for containers of thebiological material. In this connection, according to some embodimentsthe transmission of the second predetermined wavelength (being in thespectral region outside the absorption peak of the metabolic gas), isindicative of absorbance of the first wavelength by materials in theregion of interest, other than the metabolic gas. These other materialstypically have a spectral absorbance band substantially wider than thatof the absorption peak of the metabolic gas. Thus analyzing the measureddata of the transmission may include utilizing the measured transmissionof the second predetermined wavelength to process the measured data ofthe transmission of the first predetermined wavelength, which overlapsthe absorption peak. This increases the sensitivity in determination ofthe concentration of the metabolic gas and allows detection of themicroorganisms.

The high sensitivity of detection enables determination of theconcentration of the metabolic gas based on equilibrium conditionbetween a rate of generation or consumption of the at least onemetabolic gas by the microorganisms and a rate of flow of the at leastone metabolic gas into and/or out of the container. Also, in cases wherethe region of interest at which measurements are conducted is the deadspace above the portion with the biological material in the container,the high sensitivity and the use of the above mentions first and secondtypes of wavelengths may provide for eliminating a need for a-prioryknowledge of optical properties of the container.

The at least one metabolic gas may include one or more of the following:carbon dioxide, oxygen, ammonia, hydrogen sulfide, methane, ethane,butane, ethylene, sulfur dioxide, carbonyl sulfide and nitric oxide. Insome embodiments the metabolic gas includes carbon dioxide and the atleast first and second wavelengths are in a spectral regime of highabsorbance by carbon dioxide. Specifically the first wavelength overlapsone of absorption peaks of carbon dioxide in that regime, and the secondwavelength overlaps a transmission peak in the carbon dioxide spectrum.For example the spectral regime may be in a mid-IR regime (e.g. spectralregime of high absorbance by CO₂ is in the vicinity of 4.3 microns).According to some embodiments of the present invention the opticalmeasurements include spectroscopic measurements. According to someembodiments of the present invention, the illuminating the dead space(the region of interest to be measured) includes operating a broadlytunable coherent IR light source, for producing light of the abovementioned at least first and second wavelengths. The light is directedto propagate along a path of a certain predetermined optical path(length) through the dead space and, the method includes operating adetection module for detecting the light transmitted through the deadspace. In some cases, the broadly tunable coherent IR light source is aQuantum Cascade Laser (QCL). Also in some cases, operating of thebroadly tunable coherent IR light source includes modulating lightintensity in the at least first and second wavelengths, and operating alock-in amplifier (associated with the detection module) to determinethe transmission of the region of interest to the modulated first andsecond wavelengths with high signal to noise ratio signal detectionbased on the modulation.

According to some embodiments the optical measurements are applied tothe dead space of the container, while the container is remained sealedwith respect to the biological material under measurements. To this end,in some cases the container may be permeable to the at least onemetabolic gas and data about the microorganisms in the biologicalmaterial are determined based on an equilibrium condition defined bydiffusion of the at least one metabolic gas through walls of thecontainer. To this end the container may be a storage container forplatelets, such as a conventional platelets storage container.

According to some embodiments the optical measurements are applied tothe dead space of the container, where the dead space may be defined byone or more of the following: (i) a portion of the container above theportion containing the biological material; (ii) a gas chamberconfigured to be connectable to the container so as to be in the fluidcommunication with the closed container (e.g. the gas chamber may be agas outlet of the container; (iii) an extension of the dead space of thecontainer by an attached reservoir transparent to the at least first andsecond wavelengths.

In some embodiments of the present invention the container is configuredfor use in a process of fermentation. The optical measurements may beperformed through one or more optical windows optically coupled to thedead space of the container. In some cases, for monitoring thefermentation process, the optical measurements and the data analysis areperformed continuously or periodically. Accordingly the determined gasconcentration data being thereby indicative of at least one of: (a)amount of microorganisms in said container as a function of time; and(b) a rate of change in amount of microorganisms in said container as afunction of time. Thus method further includes processing the gasconcentration data to monitor the fermentation process.

According to some embodiments the method of the present invention fordetermining the concentration of at least one metabolic gas, includes:

(i) measuring IR transmission through the dead space in two or morewavelengths comprising the above noted first and second wavelengths. Themeasuring comprises: tuning a central wavelength of illuminating lighteach one of the two or more wavelengths; detecting IR light in the twoor more wavelengths transmitted through the dead space; and generatingmeasured data indicative of two or more intensity values comprisingfirst and second intensity values corresponding to the light transmittedthrough the dead space in the first and second wavelengths for a givenoptical path defined by the optical system and the dead space; and

(ii) processing the measured data based on an absorption model of the atleast one metabolic gas. The processing comprises determining a best fitbetween intensity values obtained from the absorption model and themeasured intensity values, and thereby determining the concentration ofthe at least one metabolic gas.

In some embodiments the method further includes utilizing theconcentration of the metabolic gas for estimating a degree of microbialcontamination of the biological material.

In another broad aspect of the present invention there is provided asystem for use in detection of microorganisms in a biological material.The system includes:

(a) an optical system including: a broadly tunable coherent IR lightsource and a detection module that includes a detector sensitive in theIR wavelength regime. The broadly tunable coherent IR light source isconfigured and operable for producing light in a predetermined spectrumincluding at least first and second predetermined wavelengths ofsubstantially narrow spectra corresponding to respectively an absorptionpeak of at least one metabolic gas and a spectral region outside theabsorption peak of said at least one metabolic gas. The detection moduleis configured for detecting light of the first and second wavelengthspassing through a region of interest (e.g. being a region located inbetween the light source and the detection module). The detection moduleis configured for generating data indicative of transmission of thatregion of interest to the at least first and second wavelengths; and

(b) a control system connectable to the light source and to thedetection module and configured and operable for carrying out thefollowing:

-   -   operating the light source to produce the light of at least the        first and second wavelengths. The first wavelength is selected        such that the detected transmission for the first wavelength        provides measured data indicative of absorbance by the at least        one metabolic gas in the region of interest. The second        wavelength is selected such that the detected transmission for        the second wavelength provides detection of measured reference        data indicative of absorbance of the first wavelength by        materials in the region of interest other than said at least one        metabolic gas;    -   receiving and analyzing the measured data and the measured        reference data, and generating data indicative of the        concentration of the metabolic gas in the region of interest.        This thereby enables non-invasive in-situ detection of        microorganisms in a biological material when located in fluid        communication with the region of interest. According to some        embodiments of the present invention the light source is broadly        tunable light source having a tunability range of at least 2        cm⁻¹. The broadly tunable light source may be a Quantum Cascade        Laser (QCL) with a tunability range exceeding 30 cm⁻¹. In some        embodiments, the detection module includes a lock-in amplifier,        and the control system is adapted for operating the broadly        tunable IR light source for modulating light intensity of the at        least first and second wavelengths, and operating the lock-in        amplifier to determine the transmission of the region of        interest to the at least first and second wavelengths with high        signal to noise ratio based on the modulation. To this end the        optical system is configured to define illumination and        detection paths for the light of said at least first and second        wavelengths intersecting with the region of interest for        placement, in the region of interest, a dead space, which is        free of the biological material and is in fluid communication        with a portion of a container containing said biological        material. In this connection in some embodiments the system of        the present invention may further include a mechanism for        positioning the container of the biological material with        respect to the optical system, such that the illumination and        detection paths intersect with the dead space of the container        and traverses a predetermined optical path (length) through the        dead space. It should be understood that in various embodiments        of the present invention, the system of the invention and/or its        controller (control system) may be configured and operable for        carrying out various operations of the method described above        and more also described more specifically below.

According to another broad aspect of the present invention there isprovided a method for use in detection of microorganisms in a biologicalmaterial. The method includes:

(i) applying non-invasive in-situ optical measurements to a region ofinterest being a dead space free of a biological material and in a fluidcommunication with a portion of a container containing the biologicalmaterial. The optical measurements include illuminating the region ofinterest with light of a predetermined substantially narrow spectrumincluding two or more predetermined wavelengths and measuringtransmission of said two or more wavelengths through the dead space;

(ii) analyzing measured data of said transmission and generating dataindicative of a concentration of the at least one metabolic gas in thedead space which is in fluid communication with the biological material;and

(iii) processing the gas concentration data based on an equilibriumcondition between a rate of generation or consumption of the at leastone metabolic gas by said microorganisms and a rate of flow of said atleast one metabolic gas into and out of the container, therebygenerating data indicative of microorganisms in the biological material.

According to another broad aspect of the present invention there isprovided a container including: a sealable main body for containing abiological materials and being permeable to at least one metabolic gas;and a reservoir being configured for fluid communication with the sealedmain body, and having at least a portion thereof at least partiallytransparent to one or more wavelengths corresponding to at least oneabsorption peak of the at least one metabolic gas.

According to yet another broad aspect of the present invention there isprovided a reservoir for use in inspection of biological materialcontained in a sealed platelets storage container permeable to at leastone metabolic gas. The reservoir is connectable to the container, so asto be in fluid communication with a dead space in the container (above aportion thereof where the biological material is contained) while thecontainer is maintained sealed with respect to the biological materialand contaminates/microorganisms. Also the reservoir has at least aportion thereof which is at least partially transparent to one or morewavelengths corresponding to at least one absorption peak of at leastone metabolic gas.

The present invention thus provides novel, effective and simpletechnique for accurate in-situ real time non-invasive monitoring of abiological material for detection microorganisms therein. Additionalfeatures and elements of the present invention are described in moredetails in the detailed description of embodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosedherein and to exemplify how it may be carried out in practice,embodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawings, in which:

FIG. 1A is a block diagram schematically illustration a system fordetecting microorganisms in biological material according to someembodiments of the present invention;

FIG. 1B is a graph exemplifying absorption cross section of metaboliccarbon dioxide (CO₂) gas at ambient conditions;

FIGS. 1C and 1D respectively illustrate two examples of the spectrum oflight beams of first and second wavelengths suitable for use in theinvention, where the first and second wavelengths are respectivelysuperposed to overlap/cover an absorption peak (absorption line) andabsorption valley (transmission line) of the CO₂ absorption spectrum inthe mid-IR wavelengths band near 4.3 microns;

FIGS. 1E and 1F respectively show logarithmic scale graphs illustratingthe transmittance of CO₂ for the first and second type wavelengths ofFIGS. 1C and 1D, and a ration of the CO₂ transmission in thesewavelengths;

FIGS. 2A and 2B exemplify a system for detecting microorganisms inbiological material according to some embodiments of the presentinvention, utilizing a separate closed gas chamber connected to acontainer of biological material;

FIG. 3 shows the experimental results for a measured plot of % CO₂ vs.bacterial concentration;

FIG. 4 shows simulated absorption versus wavelength and C02concentrations of the beam of the QCL in the IR spectral range 2355cm⁻¹-2410 cm⁻¹;

FIGS. 5A and 5B show experimental set ups of the system of the presentinvention used for detection of metabolic CO₂ inside a platelets productin a plastic bag utilizing direct measurement through the bag containingthe platelets (FIG. 5A) and utilizing a separate gas chamber connectedto the platelets container (FIG. 5B);

FIGS. 6A to 6D show experimental results for a fermentation process/runof recombinant protein production utilizing Escherichia coli E. Colifermentation;

FIGS. 7A and 7B show experimental results for the monitoring of plantcells growth by CO₂ online measurements performed with the device andmethod of the present invention versus standard routine measurements offresh weight (FIG. 7A) or conductivity (FIG. 7B);

FIG. 8 shows experimental results regarding the detection of carbondioxide (¹²CO₂) and an isotopologue thereof (¹³CO₂), vs time, with veryhigh sensitivity (1 ppm order); and

FIG. 9 shows experimental results comparing real-time and continuousmonitoring of carbon dioxide performed according to the presentinvention versus manual sample measurements of biomass via opticaldensity measurements (OD)

DETAILED DESCRIPTION OF EMBODIMENTS

The principles and operation of in-situ real-time and non-invasivedetection of microorganisms in biological materials according to thepresent invention may be better understood with reference to thedrawings and the accompanying description.

The inventive technique is based on measuring the absorption ofilluminating light (typically in the infrared spectrum) transmittedthrough a gaseous atmosphere in fluid communication with the biologicalmaterial, e.g. in a portion of a storage container above the biologicalmaterial. Living microorganisms produce metabolic gases such as carbondioxide (CO₂) during respiration. By means of infrared absorption, theconcentration of metabolic gases can be measured inside the storagecontainer.

Reference is made to FIG. 1A illustrating schematically in a blockdiagram a system 10 according to some embodiments of the presentinvention for detection of microorganisms in a biological material. Thesystem 10 includes an optical system which includes a tunable broadbandIR light source 12 and a detection module 15. The tunable broadband IRlight source 12 is configured and operable for emitting light in apredetermined substantially narrow spectrum. The tunable broadband IRlight source 12 is controllably operated for emitting light in at leasta first and a second predetermined wavelengths, wherein the firstwavelength corresponds to an absorption peak of at least one metabolicgas to be detected, and the second predetermined wavelength is in aspectral region outside the absorption peak of the at least onemetabolic gas. The detection module 15 includes a detector 14 sensitivein the IR wavelength regime. The light source and the detection moduleare arranged to form respectively illumination and detection paths, e.g.being in optical communication with one another, intersecting a regionof interest. The detection module is configured and operable fordetecting light in the first and second wavelengths, such as lightpassing through the region of interest located in between the lightsource 12 and the detector 14, and generating intensity data/signalsindicative of the intensity of detected light in the first and secondwavelengths. This data is therefore indicative of the transmittance ofthe region of interest to the at least said first and secondwavelengths.

Further provided in the system 10 is a control system 30 (e.g.controller), which is connectable to the optical system, i.e. to thelight source 12 and to the detection module 15. The controller 30 isconfigured and operable for operating the light source 12 to emit lightin the selected at least first and second wavelengths, and for receivingand analyzing measured/detected data/signals from the detection moduleand generating data indicative of a concentration of the metabolic gasin the region of interest.

In some embodiments, the light source 12 and the detector 14 arearranged in space-apart relationship defining the region of interesttherebetween for spectroscopic measurements. To this end, light source12 and the detector 14 are arranged such that a suitable container 24 ofa biological material 26 and/or more specifically a dead space 28associated with and being in fluid communication with such container 24can be placed. The biological material is that in which microorganismsshould be detected by optical/spectroscopic measurements performed bythe system 10 of the present invention. As indicated above, the deadspace 28 of the container is actually any space being in fluidcommunication with the atmosphere in the container above biologicalmaterial 26. This may include any one of the following: the portion 28of the container 24 above the biological material as illustrated forexample in FIG. 1A, and/or any suitable gas-chamber such as a reservoirand/or an outlet pipe/tube connected to the container and being in fluidcommunication with its atmosphere, as will be described below withreference to FIGS. 2A-2B and 5B.

The analysis of the measured data is generally based on the principlesof spectroscopy. However, in the present invention, the first and secondwavelengths are particularly selected to enable accurate andhigh-sensitivity measurements of the concentrations of one or moremetabolic gases, even in noisy environment, possibly having a wide rangeof unknown parameters. The first wavelengths is selected to be highlyaffected by absorbance by the at least one metabolic gas in the regionof interest, i.e. to overlap with the absorption line (at times termedherein as “peak”). The second wavelength is on the other hand selectedto be less affected by absorbance of the metabolic gas, but neverthelessit is selected to be spectrally close to the first wavelength, such thatit provides reference data indicative of absorbance of the firstwavelength by other materials in the region of interest. For example thedistance between the first and second wavelengths may in someembodiments be about half of distance between two absorption lines ofthe metabolic gas, or in some embodiments the second wavelength may belocated outside the spectral range including intense absorption lines ofthe metabolic gas. This is exemplified in and described in more detailsbelow with reference to FIGS. 1C and 1D.

In this regards, it should be noted that the inventors have found thatsome metabolic gases are associated with spectral regimes of highabsorbance in which sharp absorbance peaks exist in the vicinity ofsharp transmission peaks (absorbance valleys). On the contrary, theabsorption spectra of various materials (e.g. polymer, plastic of whichvarious containers are made as well as vapors such as water vapors),which are in many cases located in the optical path of the measuredgaseous media and impede accurate spectroscopic measurements of suchmetabolic gases, are typically associated with relatively broad andnon-volatile spectral profile which does not have sharp peaks. Takingadvantage of this finding, some embodiments of the invention utilize theso-selected second wavelength to provide reference to the absorbance ofthe first wavelength by materials other than the metabolic gas in thevicinity of the region of interest. This can be done because thespectral distance between the first and second wavelengths is selectedsuch, or is sufficiently small, such that the first and secondwavelengths exhibit same or nearly similar absorption by variousmaterials possibly located in the optical path.

Thus, the at least two wavelengths are specifically selected such thatthe one of them is highly absorptive by the metabolic gas to be detected(which concentration is to be measured) and the second is selected to beless absorbed by the metabolic gas but absorbed to similar level (as thefirst wavelength) by other materials conventionally/typically located inthe optical path of measurements. This allows for in situ non-invasiveoptical/spectroscopic measurements of the metabolic gas concentrationwith high accuracy and/or high sensitivity while not reducing theeffects of unknown materials/condition in the vicinity and/or in theregion of interest of the measurement.

In this connection it should be understood that in some embodiments thesystem and method of the present invention are adapted for conductingoptical measurements in more than two wavelengths; e.g. with one or morewavelengths of the first type—highly absorbed by the metabolic gas,and/or with one or more wavelengths of the second type—less/negligiblyabsorbed by the metabolic gas. More specifically a coherent broadlytunable light source (e.g. Mid-IR light source) is used to emit light atfirst type wavelength overlapping with absorption line(s) of themetabolic gas and having a spectral width wider than that of theabsorption line. In the description below the term overlapping is usedalso to denote that the spectral width of the light source exceeds thespectral width of metabolic gas (CO₂) lines. This ensures robustness andhigh repeatability of the measurements. More precisely, the spectralwidth of the light source is preferably more than the spectral width ofthe absorption line, but less than the distance between two adjacentspectral absorption lines. Thus, during a wavelength scan of thelaser/light-source, the scanning accuracy with spectral resolutioncomparable or higher than the spectral width of the light source inorder to enable to tune the light source to overlap/cover the absorptionline. The use of light source with spectral width exceeding the spectralwidth of absorption lines provides that spectral resolution of tuningneeds not to be higher than the width of the gas absorption line, whichmay be very small (e.g. wave-number below 0.05 cm⁻¹) and which spectralresolution of tuning is hard to achieve. Also, the spectral width of theabsorption line is a function of gas pressure and temperature. Henceutilizing a light source having spectral width exceeding the width ofabsorption line, decreases the sensitivity of the variations of thespectral width of the absorption lines thus improving the robustness ofthe measurements under varying conditions (temperatures and pressures).Also the condition that the spectral width of the light source is lessthan the distance between two adjacent spectral absorption lines ensureshigh contrast and/or resolution when measuring at the second typewavelength, away from the maximum absorption.

In fact, in some embodiments the light source 12 is a broad-band tunablelight source with sufficiently narrow spectral peak. The control system30 is in communication (by wires or wireless signal communication) withthe light source 12 and configured for swiping the wavelength emitted bythe light source 12 (continuously or discretely) over a certainwavelength range including several absorption peaks and/or valleys ofabsorption in the absorption spectra of the metabolic gas to bedetected. The control system is also in communication (by wires orwireless signal communication) with the detection module (e.g. foroperating it) for receiving measured data indicative of transmission ofthe several wavelengths in this spectral ranges such that one or more ofthe wavelengths correspond to the first type wavelength and one or moreof them correspond to the second type wavelength. This procedure, inwhich data on transmission of more than two such wavelengths isacquired, is used in some cases, to further improve the accuracy andsensitivity of the system and method of the present invention event invery noisy scenarios.

It should be understood, although not specifically illustrated, that thecontrol system is typically a computer system including inter aliadigital or analog input and output ports, memory, data processor, andmay be implemented as hardware and/or software modules. Such a computersystem may be at least partially integral with the detection module.

In some embodiments of the present invention, the light source 12 isconfigured for emitting substantially monochromatic light, which narrowspectral width is in the order of the width of certain spectralpeaks/features in the absorbance profile of the metabolic gas to bedetected. For example, in some cases the light source 12 is a tunable IRlight source/laser. In particular the light source may be selected to betunable within a certain wavelength band in the mid-IR regime (the termmid-IR is used herein to designate wavelengths of light in the spectralrange of 3 to 30 microns. In some particular embodiments of the system10 of the present invention the tunable quantum cascade laser (QCL) isused as the light source 12, since it provides wide wavelengthtunability and sufficiently narrow spectral width (sufficientlymonochromatic light emission). Alternatively or additionally, the lightsource 12 can also be a broadband source equipped with suitablenarrow-band spectral filters in the mid-IR regime. The use of a tunablelight source instead of the fixed wavelength source allows fordetermining the metabolic gas concentration within the container withoutusing any etalon.

The detection module 15 may include an IR detector 14 whose output isconnected to an electronic signal processor/amplifier 13. In someembodiments, the electronic signal processor 13 includes or isconstituted by a lock-in amplifier.

In some cases, the at least one first wavelength is selected to be in aspectral regime of high absorbance of carbon dioxide (being the probedmetabolic gas) such that first wavelength overlaps an absorptionpeak/line of carbon dioxide in this regime. For example the at least onefirst wavelength may be in the wavelength band in the vicinity of 4.3microns which corresponds to spectral regime of high absorbance by CO₂.Indeed, in some cases also the second wavelength is selected close tothe first wavelength and in the similar regime of high absorbance by themetabolic gas. However the second wavelength is specificallyselected/tuned to fall outside of an absorption line (e.g. in anabsorption valley) of the carbon-dioxide/metabolic gas such that it onlyprovides a reference to the absorbance by other material in this regime.

In this connection, reference is now made to FIGS. 1B, 1C and 1D, inwhich FIG. 1B shows a graph of the absorption cross section of CO₂ atambient conditions (namely pressure of 1 atmosphere and temperature of25° C.) as a function of wave number (taken from HITRAN database), andFIGS. 1C and 1D show in more details a part of this absorption crosssection of CO₂ superposed with two examples of spectral emission profileof the light source for the first and second wavelengths produced by aQCL light source. These profiles correspond to substantiallymonochromatic light beams of first and second narrow wavelength spectra.In the example of FIG. 1C the emission profile of the light source forthe first and second wavelengths respectively, overlap/cover anabsorption peak (absorption line) of the CO₂ and overlap/cover anabsorption valley (transmission line) of CO₂ in the mid-IR spectrum near4.3 microns. In FIG. 1D, as in FIG. 1C the emission profile of the firstwavelength, overlaps an absorption line of the metabolic gas, while thesecond wavelength is located outside a spectral range of intenseabsorption lines of the metabolic gas.

More specifically FIG. 1B shows the features of the CO₂ absorptionspectrum in wave-number range of near about 2300 to 2380 cm⁻¹ (i.e. formid-IR wavelength range of about 4.2 to 4.35 microns).

FIG. 1C shows in more details the absorption spectrum (graph Gco₂) ofCO₂ in the wave-number range of about 2359 to 2364 cm⁻¹ (i.e. forwavelengths ranging between 4.230 to 4.239 microns) and illustrates thetypical width of CO₂ absorption lines of about 0.07 cm⁻¹ (namely in theorder of about 0.15 nm in that wavelength range).

FIGS. 1C and 1D present narrow spectral profile (graphs G₁ in thesefigures) of a first light beam (first type wavelength) produced by atunable QCL light source 12 used in some embodiments of the presentinvention. The typical spectral width of the QCL emission is offull-width-half-maximum (FWHM) of about FWHM=0.7 cm⁻¹ (i.e. about 1.25nm), and the figures show said spectrum of the light-beam being tuned toa central wave-number of 2361.4 cm⁻¹ (wavelength of about 4234.8 nmmicrons) corresponding to the maximum of one of the absorption lines ofthe CO₂ gas.

In the example of FIG. 1C the second wavelength presented by graph G₂was tuned to central wavenumber of 2362 cm⁻¹ (wavelength of about 4233.7nm) which is in the middle between the two absorption lines of themetabolic gas. Thus, in this case the CO₂ absorption at the secondwavenumber will be much lower, than at the first one.

In the example of FIG. 1D the second wavelength presented by graph G₂was tuned to central wavenumber of 2385 cm⁻¹ (4192.9 nm). Therefore inthis example the second wavenumber is outside the spectral range/band ofhigh absorbance by the metabolic gas (e.g. outside the so called 4.3micron absorbance band of CO₂ at which main CO₂ absorption lines arepresent). Accordingly the CO₂ absorption at 2385 cm⁻¹ wavenumber is muchlower, than its absorbance at both at the 2361.4 cm-1 and 2362 cm⁻¹wave-numbers.

The transmittance of CO₂ for the above exemplified wave-numbers of thefirst and second type wavelengths is illustrated in logarithmic scale inFIG. 1E for various concentrations of the metabolic gas CO₂. Thetransmittance was simulated for a container with transparent wallsfilled with mixed N₂ and CO₂ gases at different CO₂ concentrations, atnormal pressure, normal/room temperature of 300 K, and with opticalabsorption path of 8 cm. The transmission of the first type wavelength(graph G₁ in FIGS. 1C and 1D corresponding to wave-number 2361.4 cm⁻¹)is illustrated in graph T1. The transmission of the second typewavelengths (graphs G₂ in FIGS. 1C and 1D) corresponding to wave-numbers2362 cm-1 and 2385 cm⁻¹ are illustrated in graphs T2 and T3respectively. As shown from these graphs, the absorbance of the firstwave-number in the CO₂ (graph T1) is substantially higher than theabsorbance of the second type wave-numbers (graphs T2 and T3).

FIG. 1F shows in self-explanatory manner the transmittance ratios T1/T3and T2/T3. These ratios are monotonically decreasing functions in bothcases. Accordingly in some embodiments of the present invention it maybe sufficient measure the CO₂ absorbance to obtain the value of one suchratio which is sufficient to for unambiguous determination of the CO₂concentration in the container. However, in some embodiments of thepresent invention the reliability of the measurements are furtherimproved by utilizing more than two wavelengths (e.g. to obtain morethan one such ratio). That is especially relevant for highconcentrations of CO₂ gas (exceeding few percent level) where absorptionat certain wavelengths could be very strong and measured signal veryweak.

To this end, according to the invention the controller operates/tunesthe light source to emit light in the first substantially monochromaticwavelength(s) (e.g. as illustrated in graph G₁) corresponding andoverlapping/covering the high absorbance peaks/lines of the metabolicgas such as those of CO₂ illustrated in the figure, thereby providingaccurate measurement of the CO₂ absorbance. Additionally, as notedabove, the controller operates/tunes the light source to emit light insecond substantially monochromatic wavelength(s) (e.g. as illustrated ingraphs G₂ of FIGS. 1C and 1D) corresponding to regions/valleys of lowabsorbance of the metabolic gas (e.g. transmission lines between theabsorption lines which spacing is in the order of about 1 cm⁻¹ to 1.5cm⁻¹—about 1.8 nm-2.5 nm in wavelength, and/or regions outside the highabsorbance band of the gas). These second monochromatic wavelength(s),while being narrow and tuned so as to substantially not overlap with theabsorption lines are provided for reference to the absorption ofmaterials in the optical path other than the probed metabolic gas.Further, these second wavelengths are in the general neighborhood/bandof the first wavelengths such that they provide reference data beingindicative, with good accuracy, of the absorption of the first opticalwavelength(s) in the optical path, in case the probed metabolic gas wasabsent there. In other words, the second predetermined wavelength isselected such that measured data of the transmission thereof providesreference indicative to the optical absorbance of the first wavelengthby materials other than the metabolic gas.

For example, in some cases a spectral distance between a “first type”wavelength of the emitted light and a “second type” wavelength servingfor the reference measurement (to which the metabolic gas issubstantially transmitting) is in the order of 0.5 cm⁻¹-0.75 cm⁻¹ thatcorresponds to the half of distance between two absorption lines of CO₂gas. Yet, in other case the separation distance can be of order 30 cm⁻¹for the second absorption line to be outside the whole spectral rangewith intense absorption lines. In that case this wavelength could beused as reference wavelength transmittance of light beam at thiswavelength does not depends on the concentration of CO₂, but ratherreflects absorptions of the light beam on other optical components suchas container walls transmittance. Hence, the spectral distance betweenthe first and second wavelengths is substantially small such that thefirst and second wavelengths are characterized by same or similartransmission through predetermined/conventional materials used forconventional containers of biological material.

The use of such first type wavelength(s) for the measurement ofabsorbance by the metabolic gas and the second type wavelength(s) closethereto for reference measurements allows to detect small/minute changesin the metabolic gas concentration with high sensitivity and accuracy.For example changes of 10 ppm (or 0.001%), and even as low as 1 ppm(0.0001%) in the gas concentration can be detected even in relativelynoisy environments in which various other materials such as those of thewalls of the storage-bag and/or fermentation container and/or vapors(e.g. water vapors) are located in the region of interest. The effectsof the later can be discarded with accuracy based on the referencemeasurements of the second wavelengths being close to the firstwavelengths. Consequently, the present invention allows the detection ofrelative concentrations of metabolic gas from 0 to 100% (full dynamicrange) using one single device having a sensitivity range of 1-100 ppm,preferably 1-10 ppm.

As a result of the above, in some cases the technique of the presentinvention is employed to measure metabolic gas concentrations inconventional containers such as conventional storage bags/vials forplatelets. This is achieved by taking advantage of the above describedtechnique utilizing the “first type” and “second type” (measurement andreference wavelengths) in the spectroscopic measurements. Thus, thedetection of various microorganisms in-situ in such conventional andgenerally arbitrary containers is made possible although the materialsof the container is not a-priory known, and although the container'smaterials may include materials such as polymers and/or other materials,which may be relatively opaque to the IR wavelengths used by the systemof the invention (e.g. opaque to wavelengths in the mid-IR).

As noted above in some embodiments the detection module 15 includes anelectronic signal processor/lock-in amplifier 13 that receives thesignal from the IR detector 14. Use of the lock-in amplifier enables toeven further improve the signal to noise ratio (SNR) provided by thesystem thus further improving the sensitivity and accuracy of themeasurements relating to the concentration(s) of metabolic gases andconsequently detection of microorganisms. To this end, in suchembodiments the control system 30 is adapted for operating the tunablebroadband IR light source 12 for applying time modulation to intensityof light emitted in one or more (e.g. in each) of the at least two(first and second) wavelengths, and also operating the lock-in amplifier13 to determine/measure the detected intensity(ies) of the emitted lightwith high accuracy based on that modulation. Accordingly, transmittanceof the region of interest to the first and second wavelengths (e.g. toall wavelengths used in the measurement) can be determined with highaccuracy based on the intensity modulation, while noise is mostlydiscarded as it is generally not modulated in the same way. It should benoted that the configuration and operation of various lock-in amplifiersare generally known in the art of signal processing and are thereforenot specifically described herein. A person versed in this art wouldreadily appreciate the various possible configurations of such lock-inamplifier with appropriate modulation to the emitted illumination to beused in the system of the invention.

In some embodiments, the system 10 is configured and operable forutilizing its ability to accurately detect small changes in themetabolic gas concentration, for operation in-situ and/or in real timeto non-invasively detect microorganisms in the containers/bags permeableto the metabolic gas and/or in association with one or more openings(inlets/outlets) through which in/out flow of gases may occur.Specifically, in some embodiments, after analyzing the concentrations ofthe metabolic gas in the dead space 28, the controller 30 is adapted forfurther processing the concentration of metabolic gas to detectmicroorganisms in the biological material 26.

In some cases, the detection is merely qualitative to identify whethersignificant levels/amounts of such microorganisms exist in thebiological material 26. In other cases, the detection is qualitative andis aimed at estimating the levels (e.g. amounts/concentrations) of themicroorganisms in the biological material 26.

In some embodiments the system is adapted/configured for operating inclosed containers, sealed and non-permeable to the probed metabolicgas(es). In such cases, the concentration of the metabolic gas in thecontainer is a function of the time the container is sealed and theamount of microorganisms therein during that time. Specifically, insealed container the concentration of CO₂ is increasing function withtime as long as there is biological activity inside of containerresponsible for CO₂ emission. Thus, the concentration of living cells inthat case depends on the growth history of the cells from the beginningof incubation. The correspondence between the number of cells andmeasured CO₂ concentration could be find out in that case by computingrate of changes of CO₂ concentration and correlating it with respirationrate of a single cells and the number of cells.

Alternatively or additionally, in some embodiments the container is notsealed with respect to the metabolic gas. For example, in cases ofmonitoring a biological material stored in bags or storage vials forblood components, which are permeable to the metabolic gas, and/or incases of monitoring a biological material in fermentation containersassociated with gas inlet(s) and/or outlet. Advantageously, the presentinvention allows for detecting microorganisms also in such containersin-situ and in real time without taking and sealing a sample ofbiological material from the containers and without incubating thesample (i.e. non-invasive detection). This is performed by takingadvantage of the high sensitivity and accuracy of the technique of theinvention for detecting small changes in the metabolic gasconcentration.

To this end, the controller 30 system may operate to measure themetabolic gas concentration in a dead space associated with thecontainer of biological material, while the dead space is non sealed tothe metabolic gas, and to utilize the measured concentration of themetabolic gas to detect the microorganisms qualitatively and/orqualitatively based on an equilibrium condition (e.g.balance/difference) between a rate of escape/flow of the metabolic gasfrom/into the container and a rate of generation or consumption of themetabolic gas by the microorganisms.

In cases the container is permeable to the metabolic gas, processing maybe performed by computing/estimating the microorganisms level in thebiological martial 26 based on the measured concentration of themetabolic gas diffusion of that gas through walls of the container 24.In this case, the container may be a conventional storage container forplatelets or other blood components.

Additionally or alternatively system 10 of the invention allowsreal-time in-situ detection of microorganisms in biological material 26contained in fermentation container 24 (e.g. in a container of afermentation system). To this end, the controller 30 may be configuredand operable to determine the level of microorganisms based on theequilibrium condition (e.g. balance/difference) between the rate ofescape/flow of the metabolic gas from/into the container 24 through anoutlet thereof, and a rate of generation or consumption of the metabolicgas by the microorganisms. For example that balance may be determinedbased on a difference between concentrations of the metabolic gas in agas inlet to the container 24 (e.g. the concentration in the externalatmosphere) and a concentration of that metabolic gas in the atmospherein the dead space 28 of the container, which may be a dead space of thecontainer itself (e.g. above the biological material 26) or a dead spacein fluid communication therewith, for example located at a gas outlet ofthe container. The difference in the metabolic gas concentrationscorresponds to the amount of microorganisms in the container. Moreparticularly, this is the difference that may be computed from thedifference in the amount of metabolic gas flowing in and out of thecontainer (e.g. computed by the controller 30 as the difference betweenthe products of the flow rates in the gas inlet and outlets multipliedby the metabolic gas concentration thereat respectively).

The controller 30 may utilize predetermined data of the concentration ofthe probed metabolic gas in the gas inlet (e.g. in the externalatmosphere of the container. Also the spectroscopic/optical measurementsmay be applied to a region of interest associated with thecavity/dead-space of the container itself and/or at a gas outlet fromthe container. The light source 12 and the detector 14 may be opticallycoupled to one or more optical windows exposing the dead-space to beinspected (e.g. optical windows coupled to the fermentation containerand/or to gas outlet).

In some embodiments of the present invention, the system 10 isspecifically configured for real time and continuous/periodicalmonitoring of fermentation processes. In such embodiments the controller30 may be adapted to apply continuous/periodic detection ofmicroorganisms and/or their level in the fermentation container. In thisconnection, the controller 30 may be adapted to repeatedly operate theoptical system in the manner described above to obtain, in real time,and/or repeatedly within predetermined time intervals, data indicativeof the metabolic gas concentration in the container and/or in itsoutlet. Repeatedly/continuously obtaining such gas concentration duringa period of time provides indication to the amount of microorganisms inthe container as a function of time and/or indication to the change/rateof change in this amount. The controller may be adapted to process thedata indicative of the amount of microorganisms, or the change thereof,as function of time for monitoring and/or controlling the fermentationprocess occurring in the container. For example, reference data/modelrelating to the fermentation process in a container may be utilized bythe controller to determine actions/operations to be carried out forcontrolling the fermentation (e.g. stopping the fermentation and/orchanging some of the fermentation conditions such as temperature and/orother conditions). This reference data may for example be stored in theform of a lookup table (LUT) and/or a set of one or morefunctions/models relating to the amount of micro-organisms and/or rateof change in their amount with certain actions to be carried out and/orcertain fermentation conditions to be applied/maintained.

The fermentation process monitoring/controlling can be realized usingthe a model (e.g. mathematical-model/formula and/or data) relating theamount of biomass in the fermentor with measured concentration of CO₂.The model may be pre-determined and predefined in advance and loaded tomemory and/or other storage device of the controller in the form ofdata/LUT and/or as a set of instructions soft/hard coded.

Such a model relating the amount of biomass in fermentor with theconcentration of CO₂ may be obtained/determined in advance by utilizingvarious techniques. For example, the amount of biomass may be measuredby optical density techniques (OD) and/or viable counts and/or other runparameters such as pH, RPM, TEMP, and the total volume (TV) of themetabolic gas CO₂ emitted/consumed by the microorganisms from thebeginning of the run (seeding time). The model may be a mathematicalmodel based for example on multivariable robust regression analysis.Verification of the mathematical model may be performed by number offermentation processes performed under same conditions, which areoptimal for the high product yield in the batch fermentor.

A RUN protocol, such as executable instructions and/or LUT, is then usedby the controller 30 for estimating, the amount of biomass in thefermentor based on the model's parameters and the real-time measuredconcentration of CO₂ gas and possibly other run parameters. The RUNprotocol is based on estimated values of the biomass and may includedata indicative of different aspects/actions to be taken during themonitoring of the fermentation process (e.g. conditions for addingnutrients for cell in fermentation, determining optimal inducing time(for recombinant protein production) and harvesting time, controlling pHlevel and other run aspects.

As noted above, in cases of biological containers which are not-sealedto the metabolic gas (e.g. permeable containers or containers offermentation), the bacterial growth will be reflected in real time inchanges in the metabolic gas concentration. For example, in case thebacteria are no longer alive, the carbon dioxide concentration will besubstantially equal to equilibrate with that in the air outside thestorage tank.

The concentration of metabolic gases inside a gas permeable container isdetermined by equilibrium conditions between release and rate ofdiffusion of metabolic gases through the walls of the container. Itshould be noted that in the following description containers permeableto the metabolic gas(es) are considered as an example of not-sealedcontainers with respect to the metabolic gas(es). Also, in thedescription below such permeability and diffusion of the gas from andinto the container is exemplified as relating to the permeability of thecontainer's walls. However, it should be understood that the techniquedescribed below is applicable to any other type of containers no sealedwith respect to metabolic gases, wherein the flow in and out of thecontainer may be additionally or alternatively through gas inlets and/oroutlets of the container. Further, in connection with the diffusionequations used in the description below, it should be noted that in caseof non-permeable non-sealed containers these can be substituted byproper equations taking into account other “diffusion” paths such asflow through inlet/outlet pipes and concentration of the metabolic gastherein. In other words, although the examples in the description belowmainly refers to permeable platelets bags, it should be understood thatthe technique can easily be generalized by a person versed in the artfor other types of cavities where metabolic gas may be concentrated,including the dead space in the container itself and/or that of theinlet/outlet pipes of a fermentation container for example.

The equation for gas (such as CO₂) production and transport through thewalls of a permeable container states:

$\begin{matrix}{\frac{\partial m_{{CO}\; 2}}{\partial t} = {{- {JA}} + W}} & (1)\end{matrix}$

where m_(CO2) is the mass of CO₂ gas inside the container, J is thediffusion flux from the walls of the container in units kg/(s·m²), A isthe surface of the walls exposed to the gas exchange and W is the sourceterm that describe total rate of CO₂ production inside the container. Whas units of kg/s. The diffusion flux is given by equation 2:

J=(ρ_(CO2)(t)−ρ_(CO2) ⁰)v  (2)

where, ρ_(CO2)(t) is the mass concentration of the CO₂ gas in unitskg/m³, measured at time t, ρ_(CO2) ⁰ is the ambient mass concentrationof CO₂ gas, r is the membrane permeability coefficient in units m/s.

In equilibrium,

${\frac{\partial m_{{CO}\; 2}}{\partial t} = 0},$

meaning that the CO₂ emission rate of enclosed biological material isequal to the total diffusion rate through the container walls:

W(t)=(ρ_(CO2)(t)−ρ_(CO2) ⁰)vA  (3)

If the container is sealed, then this equation is inapplicable, since nogas exchange can undergo through the container walls. In this case, theconcentration of CO₂ is gathered by Eq. (1) with the first term in theright side equal to zero:

$\begin{matrix}{\frac{\partial m_{{CO}\; 2}}{\partial t} = W} & (4)\end{matrix}$

where W(t) is the CO₂ emission rate of enclosed biological material inunits kg/s measured at time t. Taking into account that massconcentration is defined as the mass of a constituent divided by thevolume ρ_(CO2)=m_(CO2)/V, the following expression is obtained forρ_(CO2) by integrating Eq.(4):

$\begin{matrix}{{\rho_{{CO}\; 2}(\tau)} = {\frac{1}{V}{\int_{0}^{\tau}{{W(t)}{dt}}}}} & (5)\end{matrix}$

where V is the volume of the container. Since, W(t) is nonnegative,ρ_(CO2)(τ) is monotonically increasing function with time. Time t=0 inthe integral corresponds to the beginning of the run (seed time in thefermentation process).From the above equation, the following expression can be obtained formean (W(t)) CO₂ emission of enclosed biological material averaged overtime interval τ:

$\begin{matrix}{{\langle{W(t)}\rangle} = \frac{( {{\rho_{{CO}\; 2}(t)} - {\rho_{{CO}\; 2}( {t - \tau} )}} )V}{\tau}} & (6)\end{matrix}$

The change of concentration n_(CO2) can be measured by means of IRabsorption of beam of tunable IR light source such as Quantum CascadeLaser directed through the container walls. As described above, the useof the tunable source instead of the fixed wavelength source allowsdirect measurement of CO₂ concentration inside the container regardlessof container material and without use of etalon container.

The following are some examples of the technique of the presentinvention for detection of metabolic gas(es) concentration, assume thatthe container walls are at least partially transparent at the mid-IRfrequency range where strong absorption of CO₂ occurs (around 2260cm⁻¹-2390 cm⁻¹), and that the path for optical beam in the gaseousatmosphere inside the container is provided.

The dependence of % CO₂ level on the increase of bacterial contaminationwas studied experimentally. Staphylococcus epidermidis obtained from theAmerican Type Culture Collection (ATCC) were used to contaminate a bagof platelets that were collected from a single donorby apheresis. Thebacterially inoculated apheresis platelets were agitated at 22° C. andmeasurements were performed using QCL spectroscopy. The plateletcontainer was measured before and during bacterial contamination.Samples were taken from the contaminated platelet bag and a standardculture plate count was used for determining bacterial concentration[colony forming unit (CFU)/mL] in the platelet medium.

Referring now to the drawings, FIG. 3 is a plot of % C02 vs. bacterialconcentration. The bacterial concentration that was measured at thepoint where % C02 started to rise was between 1*10⁶ CFU/mL to 6*10⁶CFU/mL. The Y-axis shows % C02 level and the X-axis shows bacterialconcentration measured using standard titration analysis.

Turning back to FIG. 1A, system 10 of the present invention may be usedfor measuring the concentration of carbon dioxide in the dead space 28above the platelets 26 in a gas-permeable bag 24 that has been removedtemporarily from storage and agitation for the purpose of measuring theconcentration of carbon dioxide in dead space 28. The tunable infraredlaser 12 (for example a QCL) and an infrared detector 14 are positionedso that the light beam 20 from laser 12 is aimed at detector 14. In thisexample, the light beam 20 is focused on detector 14 by a calciumfluoride lens 18. Bag 24 is positioned between laser 12 and detector 14so that light beam 20 traverses dead space 28. Controller 30 tunes laser12 to emit light beam 20 at selected wavelengths in the vicinity of 4.3microns at a pulse repetition rate of 5 KHz, receive the correspondingresponse signals from detector 14, and analyze those signals to estimatethe concentration of carbon dioxide in dead space 28. As noted above,the signal reception and analysis portion of the controller 30 may beimplemented by a lock-in amplifier that locks onto the 5 KHz signal fromdetector 14 and displays the amplitude and phase of that signal. For anaccurate measurement of the concentration of carbon dioxide in deadspace 28 the path length of light beam 20 across the interior of bag 24is preferably at least several centimeters.

In practice, a sufficiently long optical path through bag 24 may not beavailable, and/or the walls of bag 24 may not be sufficientlytransparent at the relevant wavelengths to allow an accurate measurementof the concentration of carbon dioxide in dead space 28. In thisconnection, reference is made to FIGS. 2A and 2B illustrating twomodified configurations of system 10 that deal with these problems.System 10 is configured generally similar to that of FIG. 1A. As shownin FIG. 2A, the bag 24 may be held in place by two vertical walls 16. Indistinction to the system of FIG. 1A, in FIG. 2B a separate closed (e.g.cylindrical) gas chamber (pipe/reservoir) 40 is used and is connected tothe bag 24 using a connecting tube 50 which is by its one end connectedby fusion with a heating instrument to the bag, as is routinely done toplatelet bags in blood banks, for various reasons of their own. Suchprocedures are performed routinely without damaging the platelet bags orintroducing contamination. The other end of the connecting tube 50 isconnected to the chamber 40 that is at least partially transparent in atleast a portion thereof to the relevant wavelengths and that issufficiently rigid and long enough to provide a predetermined fixedoptical path (e.g. of several centimeters) for light beam 20. In thisspecific but not limiting example, a filter 52 is used in tube 50, thatis permeable to gases but not to liquids, and thus keeps liquids frombag 24 out of reservoir 40 but allows the gaseous contents of reservoir40 to equilibrate with the gaseous contents of dead space 28 in the bag24 so that the concentration of carbon dioxide in reservoir 40 issubstantially identical to the concentration of carbon dioxide in deadspace 28. The equilibration of the concentration of carbon dioxidebetween reservoir 40 and dead space 28 occurs sufficiently fast suchthat no special steps are needed to hasten this equilibration.Effectively, the interior of reservoir 40 is an extension of dead space28. Such connection to the separate gas chamber may be used in case therequired optical path (for detection of the specific metabolic gas)inside the container is unavailable and/or in case the container's wallstotally block the IR radiation.

In a general case, irrespectively of whether the container is sealed orpermeable with respect to the metabolic gases to be detected, thefollowing technique may be carried out by the controller 30 foraccurate, in-situ real time determination of the metabolic gas(es)concentration. IR transmission through the dead space in two or morewavelengths (comprising the above described first and secondwavelengths) is measured as described above. The measured data isprocessed by the controller 30 for example by utilizing an absorptionmodel of the at least one metabolic gas. To this end, a best fit betweenintensity values obtained from the absorption model and the measuredintensity values is performed to thereby determine the concentration ofthe at least one metabolic gas.

The following is a not limiting example of the mathematical descriptionof the measurement procedure of metabolic gas concentration inside acontainer using tunable IR light source.

The transmitted laser light intensity I(λ₀) measured on the detector isgiven by at the laser central wavelength λ₀ is given by

I(λ₀)=ηI ₀∫_(λ) _(min) ^(λ) ^(max) ƒ(λ−λ₀)e ^(−α) ^(λ) ^((cl+c) ⁰ ^(l) ⁰⁾ dλ  (7)

where I₀ is the laser intensity, η is the total intensity loss that arenot related to optical gas absorption, α_(λ) is the absorptioncoefficient (in cm⁻¹) at the given wavelength of the light λ, c is theprobed gas concentration (by volume) inside the container, c₀ is theconcentration of the probed gas outside the container in the atmosphere,l is the pathlength inside the container, l₀ is the pathlength outsidethe container between IR source and detector, ƒ(λ−λ₀) is the laserspectral distribution function around the central wavelength λ₀.

The integration limits λ_(min) and λ_(max) with λ_(min)<λ₀<λ_(max) areassumed to be such that ƒ(λ) is nearly zero outside the integrationdomain.

The absorption coefficient α_(λ) can be calculated as:

α_(λ) =nσ(λ)  (8)

where n=P/k_(B)T is the concentration of molecules and σ(λ) is theabsorption cross section in cm². The signal on the detector is assumedto be proportional to the transmittance intensity. In case of tunablelaser the central wavelength can be changed within certain range.

Thus, a model S(x, λi) for a signal on the detector can be written as

S(x,λ _(i))=b∫ _(λ) _(min) ^(λ) ^(max) ƒ(λ−λ_(i))e ^(−α) ^(λ) ^((x+c) ⁰^(l) ⁰ ⁾ dλ  (9)

where x=cl and b is a constant, x (and therefore c) can be found fromequation (11) if the measurement is done at two or more wavelengths oflight λ. In that case the unknown constant b can be excluded from theset of equations.

The concentration c can be determined from n measured values of thesignal S_(i) i=1, . . . , n at different wavelengths λ by utilizingnonlinear minimization of the model S(x, λi) as provided by functions(x) below:

$\begin{matrix}{{s(x)} = {\sum\limits_{i = 1}^{n - 1}\; \lbrack {{\log \mspace{14mu} ( \frac{ {{S( {x,\lambda_{i}} )} + \epsilon} )}{S( {x,\lambda_{n}} )} )} - {\log \mspace{14mu} ( \frac{ {S_{i} + \epsilon} )}{S_{n}} )}} \rbrack^{2}}} & (10)\end{matrix}$

where ε is a noise level at the detector. s(x) is essentially leastsquire norm of the logarithm of the ratio between measured andtheoretical signals Si and S(x, λi) at wavelength λi, i=1, . . . , n−1and the signal at λ_(η). Thus, λ_(η) is used as a reference wavelengthfor λi, i=1, . . . , n−1. The parameter c insures that function s(x) isnot singular if one of Si=0. From equation (9) the concentration c canbe determined, provided that the optical path length l is known.

The following is a specific example for using the technique of theinvention for CO₂ absorption simulations and evaluation. The simulationsof CO₂ absorption within plastic bags were performed using HITRANdatabase of CO₂ line intensities at ambient conditions and are describedabove with reference to FIGS. 1B and 1C.

FIG. 4 shows simulated absorption versus wavelength and CO₂concentrations of the beam of the QCL calculated using equation (7) inthe IR spectral range 2355 cm⁻¹-2410 cm⁻¹. The graphs H₁, H₂, H₃ and H₄correspond to the absorbed intensities for respectively 4%, 1%, 0.08%and 0% of the CO₂ concentration. As shown, the graphs have smoothbehavior of the spectra on wavelength and the transmittance increaseswhen light frequency changes from 2360 cm⁻¹-2410 cm⁻¹

Reference is made to FIGS. 5A and 5B showing experimental set ups of thesystem of the present invention for detection of metabolic CO₂ inside aplatelets product in a plastic bag utilizing respectively directmeasurement through the bag containing the platelets (FIG. 5A) andutilizing a separate gas chamber connected to the platelets container(FIG. 5B). As shown in the figures in a self-explanatory manner, the setup utilizes tunable QCL, IR detector (e.g. equipped with a CaF2plano-convex lens), lock-in amplifier detector and a controller. The QCLoperates in the pulse mode with repetition frequency of 5 kHz and pulsewidth 500 nsec. The tunability range of the QCL includes the measurementrange that was from 2361.4 cm⁻¹ till 2391 cm⁻¹. The procedure fordetermination CO₂ concentration within container may thus be as follows:the light beam is transmitted from the QCL through a small containerconnected to the plastic bag, container as shown in FIG. 2B describedabove. Signal on IR detector is measured at different wavelengths oflight λi i=1, . . . , n in the range from 2361.4 cm⁻¹ till 2391 cm⁻¹.The concentration c of CO₂ gas inside the container is estimated usingequation (10) for different using the nonlinear minimization of thefunction s(x).

As noted above in embodiments of the present invention configured formonitoring and/or controlling fermentation processes, the monitoring andcontrolling of the fermentation may be based on a model such as formulaand/or reference data relating various parameters of the fermentationincluding metabolic gas concentration with an estimation of the biomass(i.e. it amount) in the fermentation. In some cases a Linear RegressionModel is used for estimating the biomass during the fermentationprocess.

In this connection, the regression model may be pre-computed modelcalculated utilizing statistical regression analysis for modeling therelationship between one or more parameters, also considered as to aspredictor x and/or regressor variable(s), and one or more otherparameters, also referred to as response variable(s) y.

For the case of estimating of biomass in the fermentation, theregressor/predictor variable(s) (generally denoted herein x_(i)) includethe concentration C of CO₂ measured in the gases emitted from thefermenter, and/or TV being the Total Volume of CO₂ emitted from thebeginning of the run (seeding time). The response variable (generallydenoted herein y) may include the optical density OD of the biologicalmaterial in the container and l or the viable count VC (namely a measureof the count of microorganisms as typically obtained via microscopecount). In cases that multiple linear regression model is used theresponse variables—generally noted y are related to k repressor's, x₁,x₂, . . . , x_(k) according to the following formula:

y=β ₀+β₁ x ₁+β₂ x ₂+ . . . β_(k) x _(k)+∈  (11)

where βi, i=0, . . . , k, are model parameters (e.g. coefficients of themodel), x_(i) are the regressor/predictor variable(s) (e.g. parametersof the fermentation process which are independent from the responsevariable (OD in this case)), and c is the random components withsupposed mean zero and variance σ².

The regressor/predictor variable(s) x_(i) may be measured in real-timeduring the fermentation process (e.g. without sampling/extracting thematerial from fermentor and probing). For example, the total volume (TV)of CO₂ gas emitted by microorganisms vs. time may be calculated usingthe formula:

TV(t)=∫_(o) ^(t)rate×c(t)dt  (12)

where TV (t) (in liters) is the total volume of CO₂ gas emitted by thespecies since the beginning of the run (from the beginning of thefermentation process), rate is the aeration rate (e.g. measured inliters/min), and c(t) is the concentration of CO₂ (in volume fraction)measured in emission gases from the fermentor.

In this connection, it should be understood that according to someembodiments of the present invention, in addition to the CO₂concentration predictor parameter c(t), in some cases otherrun/predictor parameters/variable(s), may also be measured (e.g.continuously) to provide estimation of the response parameter(s) y withimproved accuracy. To this end the generalized formula (13) above may beused as a model defining the relation between the predictor parametersmeasured/considered x_(i) and the response parameters y. For example thepredictor parameters x_(i) may include:

RPM—agitation rate in fermentor (e.g. provided as an input from acontroller controlling the operation of the fermentation system);

RATE—aeration rate measured in liters/min (e.g. measured at the inletand/or outlets from the fermenter);

pH—acidity level in fermentor (e.g. measured by pH electrode in thefermenter)

DO—dissolved oxygen dO₂ (e.g. measured by dissolved oxygen probe in thefermenter)

Temp—temperature in fermentor,

FIG. 6A is a table illustrating several of the above predictorparameters measured/obtained during an experiment of a fermentationprocess/run of recombinant protein production utilizing Escherichia coliE. Coli fermentation. The recombinant proteins are widely used inbiotechnology and medical applications as vaccines and proteintherapeutics, and as industrial enzymes for detergents and fuel ethanolproduction. Such recombinant protein products are made by inserting thegene that encodes the desired protein into a host cell (bacteria, yeast,insect, or animal cells) capable of producing this protein. FIG. 6Bshows graphs OD_(g) and TV_(g) illustrating respectively the measuredoptical density—OD and the total volume of CO₂ emission—TV, as afunction of time. OD and TV were measured during a fermentationexperiment. As shown the OD is increased from 1 to about 55 during thefirst 10 hours of the experiment. Then it gradually continues to grow upto values of 75 during the next 12 hours of experiment. TV was measuredcontinuously while OD at 15 time points as specified in the table inFIG. 6A. The correlation coefficient between OD and TV is 94.4%.

FIG. 6C is a graphical illustration showing two regression and referenceplots, RG and RF, corresponding to the optical density of a biologicalmaterial as a function of time. Plot RF is a reference plot obtained bydirect measurements of the optical density taken during the experimentalfermentation run. The regression plot RG is obtained during theexperimental fermentation run by processing the measured CO₂concentration based on the regression model which is used according tothe present invention. As shown in the graphs the OD results obtained bythe regression model based on the CO₂ concentrations are similar andalmost same as those obtained by direct OD measurements.

The parameters of the regression model are estimated by means of therobust regression algorithm based on equations 11 and 12 as describedabove. More specifically, the robust regression operates by assigning aweight to each data point. Weighting is done automatically anditeratively using a process known as iteratively reweighted leastsquares. In the first iteration, each point is assigned equal weight andmodel coefficients (pi in equation 11 above) are estimated usingordinary least squares. At subsequent iterations, weights arerecomputed, so that points, which were farther from model predictions inthe previous iteration, are given lower weight. The model coefficientsare then recomputed using weighted least squares. The process continuesuntil the values of the coefficient estimates converge within aspecified tolerance.

The regression model used in this experiment utilizes the followingregression coefficients βi between response variable OD (y in equation11 above) and the regressor/predictor variables (x_(i) in equation 11above) including: C, TV, RPM, pH and TEMP. To this end the followingregression model was used for the estimated model parameters forprediction of OD from the measured values of CO₂ concentration andadditional measured parameters of the fermentation process (theestimated OD being indicative of the biomass amount):

OD=0.38+0.17*TV+2.06*C+0.0013*(RPM-50)+22.07*(pH-7.0)−0.95*(TEMP-37)  (13)

FIG. 6D shows the experimental results for a measured plot P1 of CO₂concentration (left y axis) and the plot P2 of OD (right y axis) as afunction of time. As shown in the figure there is a correlation betweenthe OD and CO₂ measurements through during first 325 minutes of theexperiment. Then, due to stress in carbon source, thebacteria/microorganisms keep growing with alternative metabolic cycles,as seen in CO₂ concentration plot P1. When the biomass/microorganismsdie, the CO₂ decreases while the OD parameter stays constant.

FIGS. 7A and 7B show plant cells growth monitoring by CO₂ onlinemeasurement made with the device and method of the invention versusfresh weight or conductivity measurements. The measurements have beenconducted for plant cells in disposable fermenters. The high resolutionof the device of the invention (1 ppm sensitivity) and continuous (realtime) CO₂ measurements show a very high correlation with cellproliferation as measured by standard methodologies (fresh weight orconductivity). FIG. 7A shows the total volume of CO₂ gas emitted byplant cells vs time, during the whole experimental run correlates withfresh weight. Time=0 is the seeding time. The total CO₂ is correlatedwith the biomass and growth rate. This quantity was calculated usingformula (14):

V(t)=rate×∫_(o) ^(t) s(t)dt  (14)

where V(t) (in L) is the total volume of CO₂ gas emitted by the cellssince the beginning of the run, rate is the aeration rate (in L/min),s(t) is the concentration of CO₂ (in volume fraction) measured inemission gases from the bioreactor. s(t) does not contain the initialconcentration measured at the beginning of the run prior to the seedingtime, which was subtracted from s(t). FIG. 7B shows the % concentrationof CO₂ gas emitted by plant cells vs time, and correlation withconductivity, during the whole experimental run.

FIG. 8 shows experimental results demonstrating that the device andmethod of the invention can be employed for detecting isotopologues of ametabolic gas, such as carbon dioxide, with a very high sensitivity. Inthis experiment the presence of people in an office was monitored duringfive days based on the concentration of ¹²CO₂ and ¹²CO₂. The resultsshow that late afternoon, when people were leaving, the totalconcentration of CO₂ was decreasing while, in the morning, the totalconcentration of CO₂ was increasing. It also shows that the device ofthe invention was able to detect variations of ¹²CO₂ concentration inthe air between 0 and 0.07% (below 700 ppm), but also very slightvariations of ¹³CO₂ concentration in the ppm order, namely between 0 and7 ppm (about 1% of the total concentration of CO₂ is composed ofisotopologue ¹³CO₂). For the sake of clarity, the curve showing theconcentration of ¹³CO₂ has been represented with a ×100 scale.

FIG. 9 shows experimental results demonstrating the advantages of theonline and continuous monitoring of bacteria growth via detection ofcarbon dioxide concentration by the method and device of the invention(continuous line) versus periodic optical density manual measurements(dashed line). The lag phase (first 1.5 h) and log phase (1.5 h-3 h) canbe clearly seen with the method of the invention but not with ODmeasurements. Furthermore, IPTG induction at h=3 and its blocking effecton bacterial replication can be clearly monitored (time during which theprotein of interest is produced). Routine OD measurements were taken 4times to monitor the fermentation process (at about h=1.75, 2, 16.25 and17.75) while the method and device of the invention enable a continuousmonitoring of the bacterial population. Thanks to the present method, ithas been shown that bacterial replication restarted at h=10 and that afurther IPTG induction would have been possible to optimize theproduction process.

Thus, the present invention provides novel, effective and simpletechniques for accurate in-situ real time non-invasive monitoring of abiological material by monitoring metabolic gases in the dead spaceassociated with the biological material. The biological material thatcan be monitored/inspected utilizing the invention includes but is notlimited to sugars, proteins, or nucleic acids, or a combination of thesesubstances. They may also be living entities, such as cells and tissues.They may be made from a variety of natural resources—human, animal,plant and other microorganism—and may be produced by biotechnologymethods. Example of biological product is blood transfusion productssuch as RBC, platelets and plasma. The biological materials may includefood product (food microbiology products). Bacterial viabilitydetermination is one of the major concerns in the food industry becauseinjured bacteria cause a significant health threat if they revive duringfood distribution and storage and it is important to examine theefficacy of various intervention treatments used in food processing.Also, the invention provides for effective monitoring of a fermentationprocess, where micro-organisms are exploited to produce a wide varietyof products such as dairy products (cheese, yogurt), beverages (beer,wine), single cell proteins (SCP), antibiotics, chemicals (citric andacetic acid, amino acids, enzymes, vitamins), fuels (ethanol, methanol,methane). Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention as hereinbefore exemplified without departing from the scopethereof defined in and by the appended claims.

What is claimed is:
 1. A method for measuring metabolic gasconcentration, comprising: applying, via a tunable coherent infraredlight source, an infrared light beam to a region of interest, whereinthe region of interest is positioned between the tunable coherentinfrared light source and a detection module, wherein the region ofinterest is in fluid communication with a biological material includingliving cells emitting a metabolic gas; measuring, via the detectionmodule, a plurality of signals based on the application of the infraredlight beam to the region of interest, wherein measuring each of theplurality of signals further comprises tuning the tunable coherentinfrared light source; and determining the concentration of themetabolic gas based on the plurality of signals.
 2. The method of claim1, the plurality of signals including a first signal, wherein the firstsignal is captured when wavelengths of the infrared light beam overlapwith an absorption peak of the metabolic gas.
 3. The method of claim 2,the plurality of signals further including a second signal, wherein thesecond signal is captured when wavelengths of the substantiallymonochromatic infrared light beam overlap with a transmission peak ofthe metabolic gas.
 4. The method of claim 3, wherein the infrared lightbeam has a first central wavelength when the first signal is measured,wherein the infrared light beam has a second central wavelength when thesecond signal is measured, wherein a distance between the first centralwavelength and the second central wavelength is less than a distancebetween two adjacent absorption peaks of the metabolic gas.
 5. Themethod of claim 3, wherein wavelengths of the infrared light beam whenthe first signal is measured are more absorptive of the metabolic gasthan wavelengths of the infrared light beam when the second signal ismeasured.
 6. The method of claim 1, wherein the infrared light beam is asubstantially monochromatic infrared light beam.
 7. The method of claim1, wherein the biological material is enclosed in a sealed container,wherein the concentration of the metabolic gas is determined basedfurther on a gas concentration of an area inside the sealed containerand a gas concentration of an area in fluid communication with thesealed container.
 8. The method of claim 1, wherein the biologicalmaterial is subject to a fermentation process, further comprising:determining at least one action for controlling the fermentation processbased on the determined concentration of the metabolic gas.
 9. Themethod of claim 1, the measurement of the plurality of signals and thedetermination of the concentration of the metabolic gas are performedany of: continuously, and repeatedly.
 10. A non-transitory computerreadable medium having stored thereon instructions for causing aprocessing circuitry to execute a process, the process comprising:applying, via a tunable coherent infrared light source, an infraredlight beam to a region of interest, wherein the region of interest ispositioned between the tunable coherent infrared light source and adetection module, wherein the region of interest is in fluidcommunication with a biological material including living cells emittinga metabolic gas; measuring, via the detection module, a plurality ofsignals based on the application of the infrared light beam to theregion of interest, wherein measuring each of the plurality of signalsfurther comprises tuning the tunable coherent infrared light source; anddetermining the concentration of the metabolic gas based on theplurality of signals.
 11. A system for measuring metabolic gasconcentration, comprising: a processing circuitry; and a memory, thememory containing instructions that, when executed by the processingcircuitry, configure the system to: apply, via a tunable coherentinfrared light source, an infrared light beam to a region of interest,wherein the region of interest is positioned between the tunablecoherent infrared light source and a detection module, wherein theregion of interest is in fluid communication with a biological materialincluding living cells emitting a metabolic gas; measure, via thedetection module, a plurality of signals based on the application of theinfrared light beam to the region of interest, wherein measuring each ofthe plurality of signals further comprises tuning the tunable coherentinfrared light source; and determine the concentration of the metabolicgas based on the plurality of signals.
 12. The system of claim 11, theplurality of signals including a first signal, wherein the first signalis captured when wavelengths of the infrared light beam overlap with anabsorption peak of the metabolic gas.
 13. The system of claim 12, theplurality of signals further including a second signal, wherein thesecond signal is captured when wavelengths of the substantiallymonochromatic infrared light beam overlap with a transmission peak ofthe metabolic gas.
 14. The system of claim 13, wherein the infraredlight beam has a first central wavelength when the first signal ismeasured, wherein the infrared light beam has a second centralwavelength when the second signal is measured, wherein a distancebetween the first central wavelength and the second central wavelengthis less than a distance between two adjacent absorption peaks of themetabolic gas.